Hydrocarbon oil treatment



May 10, 1938. 0. L. ROBERTS HYDROCARBON OIL TREATMENT Filed Nov. "5, 1934 mw mm m H m. x K \E V hm gm x\ A Q lfi NW mw k NW ll .IIHHH H WHH I H" \II J mm A fi W. W Wm s y r 0 M 1b 1a m A w L .w G 8 w o M k% B M J E w x Q MN inn-M mmy.- Ww m\ (N M-Au Patented May 10, 1938 PATENT ZOFFICE OIL Oscar L. Roberts, Merwood Park, Pas alsignor to The Atlantic Refining Company, Philadelphia,

Pa., a corporation oi Pennsylvania Application Novembcr s, 1934, Serial No. 151,315 5 Claims. (01. 196-13) The present invention relates to a process of obtaining countercurrent contact between partially immiscible liquids, and particularly to the extraction of components fromhydrocarbon oils with a solvent which will selectively dissolve such components.

Heretofore, it has'been found that certain selective solvents, as for example, nitrobenzene, phenol, and aniline and the like, may be used to 1 eifect the separation of a hydrocarbon oil, such as petroleum, into fractions of substantially the same boiling range but of different chemical compositions and of diflerent physical properties. The difference in physical properties of the fracil tions so produced, i. e., the degree of parailinicity or naphthenicity of the said fractions, may be expressed by the relationship of viscosity to gravity, for any particular oil. The viscosit -gravity constant, as developed by Hill and Coats in an 9 article in Industrial and Engineering Chemistry, volume 20, page 641, 1928,'will be used herein to indicate the degree of parailinicityand of naphthenicity of the oil or oil fractions; the lower the value of the constant, the higher the degree of g paraiilnicity of the oil.

In accordance with the prior practice in the field of ccuntercurrent solvent extraction, it has been customary to employ substantially the same temperature in each of the stages of a counterno current extraction system or to employ a temperature gradient thruout the successive stages of such system. For example, in a stage countercurrent system operated in accordance with the method first mentioned, each of the stages may 85 be maintained at a temperature of the order of C., or according to the second method, an increasing or decrea'sing temperature gradient of 5 C, between each stage maybe maintained.

I have discovered that by adjusting the tem- 40 peratures of the various stages so that the temperature of any stage is higher or lower than either of the stages next to or contiguous to the specified stage, I am able to obtain an increased yield of desirable oil of a given quality or the same 45 yield of oil of a better quality than can be obtained in accordance with the prior processes. For example, in operating a 3 stage countercurrent extraction system employing a solvent such as nitrobenzene, I may maintain the 1st stage, 50 i. e., that stage in which the oil stock is introduced in contact with partially used solvent, at a temperature of the order of 5 0.; the second stage at a temperature of 15 C., and 3rd stage, i'. e., that from which the refined oil is discharged, at 55 a temperature of 5 0.

It is believed that the type of temperature adjustment which I employ causes oil dissolved in some stages to be thrown out of solution in some preceding stages and sent in the direction of the stages in which such oil was dissolved. My process may be likened to that in a fractionating column in which the lower temperature' stages function as dephlegmators to produce recycle or reflux oil which aids in increasing the efficiency of fractionation.

i For purposes of illustration, reference is made to the accompanying drawing which shows diagrammatically, one form of apparatus suitable for carrying on my process:

In the drawing, a series of alternate mixing vessels 6, ll, and "and settling vessels II, i8, and '24 are disposed in step-like arrangement, the mixing vessels being provided with paddle stirrers I, I, and 1" respectively, or other suitable mixing devices, means for-introducing thereinto oil and solvent, and means for passing the mixture therefrom into the respective settling vessels. The settling vessels are provided with heating and/or cooling coils l2, l2, and I2" and means for passing undissolved oil to succeeding and sola vent containing dissolved oil to preceding mixing vessels. The system is equipped with low pressure pumps, feed lines and heat exchangers so arranged as to maintain a regulated countercurrent flow of oil and solvent through the exw traction stages, the heat exchangers 4, 9, i3, i6, i9, 22, 28, 32, and 36 controlling the temperatures of the oil and solvent streams, and indirectly the temperatures in the mixing and settling vessels.

In the operation of my process. I may choose, for examplenitrobenzene as the selective solvent andalubricating oil as the stock to be selectively extracted. The 011' stock supplied from a storage vessel (not shown) is drawn thru valve-controlled pipe I, by means of pump 2, and is passed 40 thru pipe 3 and heat exchanger 4 wherein it is cooled to the desired temperature, for example, 5 C. The cooled oil is then passed thru pipe 5 into mixing vessel 6. The selective solvent, 1. e.,

nitrobenzene, is conducted from a storage vessel (not shown), thru valve-controlled pipe 28, and

is passed by means of pump 21 thru heat exchanger 28 wherein it is cooled to the desired temperature, for example, 5 C. The cooled solvent is then passed thru pipe 29 into mixing 5 vessel 20. After sufllcient oil stock and solvent have been supplied to the system, a continuous countercurrent flow will be set up and the extraction process will commence to function. The oil stock charged to the mixing vessel 8, and the partially spent solvent from the bottom of settling vessel l8, which flows thru valve-controlled pipe 34 and is forced by'pump 35 thru heat exchanger 36 wherein it is cooled to about 5' C., is passed by means of pipe 31 into the mixing vessel 6, wherein it is contacted with the oil stock by agitation with the stirrer I. The mixture of oil and solvent is passed thru valve-controlled pipe 8, heat exchanger 3 and pipe l into the settling vessel ii and a separation of undissolved oil and solvent containing dissolved oil is eiTected at a temperature of about C., the undissolved oil comprising the upper layer, and the solvent containing the dissolved oil the lower layer. The lower layer of spent solvent containing dissolved oil iswithdrawn from the system by means 01' valve-controlled pipe 38 and the solvent and oil may subsequently be separated by distillation. The undissolved oil layer, containing a small quantity of solvent, occupies the upper portion of the settler I l and flows by gravity thru heat exchanger I3, wherein it is heated to a temperature of, for example, 15 C., and thence into the mixingvessel l4. Vessel I4 is simultaneously supplied with partially spent solvent from the lower section of settler 24, which solvent flows thru valve-controlled pipe 30 and is forced by pump 3| thruheat exchanger 32,

wherein it is heated to about 15 C. and thenceis passed thru pipe 33 into said mixing vessel l4. The oil and solvent are herein again thoroughly contacted by means of stirrer I, and the mixture of oil and solvent is passed by valve-controlled pipe l5 thru heat exchanger l6 and pipe ll into settling vessel I! wherein the separation into undissolved oil and. solvent layers is efl'ected at a temperature of about 15 C. The lower layer of solvent containing dissolved oil is withdrawn from settler l8 thru valve-controlled pipe 34 andis pumped thru heat exchanger 36 and pipe 31 into mixing vessel 6, as hereinbefore described. The undissolved oil layer in the upper portion of settler l8 flows by gravity thru heat exchanger 19, wherein it is cooled to a temperature of the order of 5 0., and thence into mixing vessel 20. Vessel 20 is simultaneously supplied with fresh solvent from a storage vessel (not shown), which solvent is passed thru valve-controlled pipe 26 and forced by pump 21 thru heat-exchanger 28, wherein it is cooled to about 5 C. and thence passed by means of pipe 29 into said mixing vessel 20. The oil and fresh solvent are herein thoroughly contacted by means of stirrer T". and

the mixture of oil and solvent is passed by valvecontrolled pipe 2| thru heat exchanger 22 and pipe 23 into settler 24 wherein the separation of undissolved oil and solvent layers is effected at a temperature of about 5 C. The lower layer of solvent containing dissolved oil is withdrawn from settler 24 thru valve-controlled pipe 3. and is passed to mixing vessel I 4 as previously described.

The upper layer of undissolved oil containing a.

1st stage as eiiected at 5 C.; the 2nd stage at 15 C. and the 3rd stage at 5 C., I may operate the mixing vessels at temperatures of complete miscibility and thereafter adjust the temperatures of the mixer eilluxes by means of heat exchangers 9, l6, and 22 prior to passing such eflluxes to their respective settlers, which may operate at the aforementioned temperatures. Furthermore, while I have given the temperatures of 5 C., 15 C. and 5 C. as exemplary of suitable operating temperatures, I do not intend to limit myself thereto, but may employ various combinations of temperatures, depending upon the number of stages comprising the system, the character of the solvent and oil stock, the ratio of solvent to stock and the quality of the oil product desired. In the operation of a multi-stage system where the temperature of any particular stage is higher than that of either of the stages immediately adjacent thereto, such higher temperature stage may be sub-divided into substages, each sub-stage being maintained at the same or higher temperature than the preceding sub-stage.

I do not intend to confine myself to a system comprising any definite number of stages, but

contemplate as within the scope of my invention, any batch countercurrent system of 3 or more stages, or a continuous countercurrent system in a single stage, provided with alternate heating and cooling means. The following table will serve to illustrate the various temperature combinations which may be applied to a system of, for example, '7 stages.

Table 1 2nd Stage 3rd Stage 4th Stage 5th Stage 6th Stage 1st Stage stage Table 2 Temperature 0! m1 Stages Undissolved oil fraction Percent S yield Vis.-grav. 1st 2nd 3rd constant Tables 3 and 4 present a comparison of the results obtained in operating a 3 stage batch countercurrent system in which the temperature of each stage is the same, in contrast to the operation of the same system in which the temperature of the intermediate stage is higher than that of either of the adjacent stages. Nitrobenzene is employed as the solvent and the stocks treated were a vacuum distillate from a Mid-Continent crude oil and a residuum from Oklahoma crude 011 respectively.

Table 3 Temperature Percent stages Undissolved oil traction solvent bastedkon P tSUi API Vi soc orcen .vs. s.-grav 2nd yield 210 r. gravity wnstent C. C. G. 100.0 211" 21. 7 0. 840 200 25 25 25 46.5 141 27.9" 0.799 200"..." 25 50 25 $0.0 l37" 27.9 0790 Table 4 Temperature Percent 0! an 8mg Undissolvedoiliiraction solvent tg l P tSUi APIVigra B 0 H081! .VS. S.- V- 1st 2nd 3rd yield @210"!. gravity constant C'. C'. C. 100. 0 142" 2!). 2 0. 858 160 5 5 6 55.0 W 212 0.810 150 0 25 5 58.7 95" 27.7 0.808

It will be seen from the above tables, that, by my process of varying the temperature upwardly and downwardly from stage to stage in the extraction system, I am able to obtain an increased yield of oil of a given quality or the same yield 01' oil of better quality than may be obtained in accordance with the processes of the prior art.

The extent of the variation between temperatures in the different stages of the treating apparatus will vary with difierent oil stocks, solvents, etc., but in general is at least 5 C. between' zones of different temperatures and in some instances may be 10 C. or more. In many cases it is desirable that the separating temperature in nonadjacent stages be substantially equalor at any rate should differ by not more than 5 or 10 C. The temperature of an intermediate stage should be removed from either of the nonadjacent stages by an amount at least as great as the variation between said nonadiacent stages.

While I have described my process in connection with the employment of nitrobenzene as a selective solvent, I do not intend to limit myself thereto, but may use any selective solvent or mixture of solvents, including, for example, any one or more of those mentioned by Ferris, Birkhimer and Henderson in their article appearing in Industrial and Engineering Chemistry, vol. 23, p. 753 etc. (1931).

What I claim is:

1. The process 01' extracting a hydrocarbon oil with a selective solvent, which comprises passing oil in countercurrent contact with the solvent through a plurality oi extraction zones while maintaining the temperature in two non-adj scent zones substantially uniform with respect to one another and the temperature in a zone located between said two non-adjacent zones substantially diflerent from the temperature in either of said two non-adjacent zones.

2. The process of extracting a hydrocarbon oil with a selective solvent, which comprises passing oil in countercurrent contact with the solvent through a plurality of extraction zones while maintaining the temperature in two non-adjacent zones within about 5 C. of each other and the temperature in a zone located between said two non-adjacent zones at least 5 C. different from that in either of said two non-adjacent zones.

3. The process of extracting a hydrocarbon oil with a selective solvent, which comprises passing oil in countercurrent contact with the solvent through a plurality oi extraction zones while maintaining the temperature in two non-adjacent zones within about 10 C. of each other and the temperature in a zone located between said two non-adjacent zones at least 10 C. different from that in either of said two non-adjacent zones.

4. The process of extracting a hydrocarbon oil with a selective solvent, which comprises passing oil in countercurrent contact with the solvent through a plurality of extraction zones while maintaining an intermediate zone at a higher temperature than either of the zones adjacent thereto.

5. The process oi extracting a hydrocarbon oil with a. selective solvent, which comprises passing oil in countercurrent contact with the solvent 

